All the components in a room are what make the space interesting. Furniture, lamps, paintings and other accessories all work in concert. It is the same concept outside with landscape design.
There are multiple components working together to define an outdoor space. Sometimes the difference between very nice and absolutely awesome can be one missing component. When I am looking for absolutely awesome as part of landscape design I make sure container plantings are part of the whole.
If you reference the picture here, the small private patio works nicely with the deck and the view of the lake in the background can make you envious. But what helps pull the space together are the container plantings.
There are 15 containers filled with annuals in this photo for those who are counting. No specific container is dominant in this scenario. I could have taken the opposite approach and used two or three large urns to achieve the goal just as effectively. But without the container gardens in either approach the view would be diminished.
When your patio or outdoor room looks a little drab, step back and ask yourself if containers would make a difference. They are part of an integrated approach to landscape design and part of what makes a space spectacular.